Pressure sensors manufactured using MEMS (micro-electro-mechanical systems) technology are used as, e.g., pressure sensors or pressure switches in industrial machines. These pressure sensors include a diaphragm, as a pressure receiving portion, which is formed by, e.g., partially thinning a substrate. The pressure sensors detect stress or displacement generated when the diaphragm is deformed under pressure.
One example of a pressure sensor is a pressure sensor formed by bonding two substrates together. In order to manufacture the pressure sensor disclosed in a related art, a LOCOS oxide film is first formed on the surface of a first substrate to surround a predetermined region. A second substrate is bonded to the surface of the LOCOS oxide film. In the predetermined region, therefore, a space is formed between the first and second substrates. Then, the opposite surface of the first substrate from the surface formed with the LOCOS oxide film is cut and abraded until the LOCOS oxide film becomes exposed. As a result, the residual portion of the first substrate surrounded by the LOCOS oxide film becomes a diaphragm.
A capacitance type pressure sensor is obtained by forming electrodes in the first substrate (the diaphragm portion) and the second substrate (the portion facing toward the diaphragm portion).
In the prior art set forth above, the manufacturing cost grows higher because two substrates are needed to manufacture one pressure sensor. Since the pressure sensor has a thickness close to the thickness of the two substrates, the volume of the pressure sensor as a whole becomes greater. Moreover, the need to use two substrates in manufacturing one pressure sensor leads to an increase in the number of steps for manufacturing the pressure sensor. Particularly, in order to manufacture a capacitance type pressure sensor through the use of two substrates, it is necessary to form electrodes in the first substrate having a diaphragm and a second substrate having a portion opposing to the diaphragm across a space.